Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations, the description reveals the important behavioral consequence that customerId is bound to :customer_id in every widget query, and clarifies that no access is granted by adding a customer. It also discloses the plan-limit constraint. It does not mention duplicate-add behavior or error conditions, but the annotations already signal non-idempotent, non-readonly behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is four short sentences, each earning its place: the core action, the customerId matching constraint and its consequence, the access caveat with an alternative, and the plan-limit condition. There is no fluff or repetition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple three-parameter create-like tool with no output schema, the description covers the purpose, the critical identifier binding, the access boundary, and the plan limit. It does not describe duplicate customerId handling or success/error output, but these are minor for an agent deciding whether and how to call it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema already covers all three parameters at 100%, so the baseline is 3. The description adds meaningful extra semantics for customerId—it must exactly match a value in the caller's own database and is bound to :customer_id in widget queries. The other parameters rely on their already-sufficient schema descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific action and resource: 'Add one of your customers to a multi-customer dashboard.' It also distinguishes itself from the sibling add_customer_user by explicitly noting that adding a customer does not grant access, so the agent can tell them apart.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives clear context for when to use the tool, names the alternative for access-granting ('use add_customer_user for that'), and states an eligibility condition ('Subject to your plan's customer limit'). This is explicit when/when-not/alternatives guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.